With the advent of EFI (Electronic Fuel Injection) there was a need to improve troubleshooting this complex system...and expand on the ECM (Electronic Control Micro-Processor Module), using a more complete instruction set and subsequent codes to assist troubleshooting. Don't know if it applies to your 2002 Heritage, but you may want to find out if your speedometer can initiate this procedure...

Sorry for the error regarding link for retrieving codes on earlier HD models, the instruction set was more limited, on the earlier models. Like Smitty says, some of the codes only give symptoms and are somewhat cryptic like XXXX "out of range" may mean area of trouble cannot be read because no reading is available (possibly an open wire or sensor being monitored).

So as Smitty & TQ provided you with some very good info...do be careful when accessing connector(s) and not short or ground out pins...! You may also be wondering why there is no info in your HD Service Manual...this is because the HD Electrical Diagnostic Manual is a separate book for...you guessed it, the princely sum of $65 MSRP. Just another tool in your troubleshooting toolbox...:s

With the ability to check the codes without any special reader, is there any reason to check the codes (any specific) if bike appears to be running good. Preventative maintenance?

Click to expand...

On a 2010,,, absolutely. There are current & historical codes. An issue that was detected "at one time" but is not present with this key cycle is a historical code which is something you want to keep an eye on.

If I was throttle by wire I would be concerned for any codes such as P2138, P2128, P2127, P2123, P2122, etc. Any codes that have to do with miss- communication from the throttle body servo motor to the twist grip would be my #1 concern. The rest of the codes are important but not like the TBW ones are.

But that is just my opinion. I am sure some will say "limp mode" will kick in if something goes wrong. For those that believe that, all I can say is "Ok"..